moves Productor into impl { }
moves Productor into impl { }

jkhoogland/cppitertools,ryanhaining/cppitertools,tempbottle/cppitertools,tempbottle/cppitertools,tempbottle/cppitertools,jkhoogland/cppitertools,ryanhaining/cppitertools,ryanhaining/cppitertools,jkhoogland/cppitertools